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PALB2 gene mutations may increase breast cancer risk

The PALB2 gene made news recently when researchers found that its mutated form is associated with a surprisingly high risk of breast cancer. Women with a PALB2 mutation have a 35 percent risk of developing breast cancer by age 70. The risk for women younger than 40 was eight to nine times that of the general population.

Breast cancer risk is typically linked to mutated BRCA 1 and BRCA 2 genes, which are the most common inherited causes of the disease. Women have a 50-70 percent chance of developing breast cancer with a mutated BRCA1 gene and a 40-60 percent chance with a mutated BRCA2 gene. Looking at the low end of the spectrum, the PALB2 gene is not far behind in the risk it imparts.

The PALB2 gene—“the new breast cancer gene”—was originally thought to be a partner gene to BRCA2. If the PALB2 gene has a mutation, it cannot function properly. As a result, the BRCA2 gene also cannot function properly to help protect against cancer. We now know that PALB2 also interacts with BRCA1. So, if a woman has a PALB2 mutation, she has risks for the same cancers—breast and ovarian—associated with BRCA1 mutations.

The researchers looking into the PALB2 gene studied 362 members of 154 families known to have PALB2 mutations. In these families, women not only had an increased risk of developing breast cancer but the risk seemed to be higher if other family members had been diagnosed with breast cancer. While the average woman has a 12 percent risk of developing breast cancer by age 70, their study published in The New England Journal of Medicine found a 35 percent risk for women with a PALB2 mutation.

Women with PALB2 mutations should have increased screening for breast cancer with mammograms and breast MRI. If a woman has family members with breast cancer, screening should start before the recommended age of at least 40. We recommend women start screening 10 years earlier than the age of the youngest family member diagnosed with breast cancer.

Mutations in the PALB2 gene also were associated with increased risk of pancreatic cancer in some of the families and an increased risk for male breast cancer. How much increased risk for each has not been determined yet. The study also did not confirm an increased risk for ovarian cancer, so additional research is needed to determine these risks.

Since the BRCA genes were discovered in 1994 and 1995, we have learned that at least 16 additional genes may contribute to breast cancer risk. With the development of next generation gene sequencing, we are now able to test for a panel of genes that may increase the risk for hereditary cancers. Learning that you have a mutation in any one of these genes can help you take steps to protect yourself and your family members against the associated cancers.